Process for bleaching flour



Jan. 5, 1943.

H. M DONALD PROCESS FOR BLEACHING FLOUR Filed May 5, 1941 2 Sheets -Sheet 1 fiver 0507* W fliiorryeys Jan. 5, 1943 H. MCDONALD 2,307,631

PROCESS FOR BLEACHING FLOUR Filed May 3, 1941 2 Sheets-Sheet 2 Aiiorrzeys Patented 5, 1943 PROCESS roa BLEACHING FLOUR.

Hugh McDonald, Minneapolis, Minn., assignor to Pillsbury Flour Mills Company, Minneapolis, Minn. a corporation of Delaware Application May 3, 1941, Serial No. 391,735

9 Claims. (Cl. 99-232) This invention relates to processes and apparatus for bleaching flour and other analogous powdered material.

It is a common practice at the present time in the flour industry to bleach flour by subjecting the same to the action of a bleaching gas such as chlorine gas. As the bleaching process is at present carried out there is an opportunity for the flour to lodge on the walls of the bleachin apparatuscausing over-treatment of the lodged flour, necessitating frequent clean out of the bleaching apparatus and also often causing admission of over-treated lumps of flour in the flour stream.

It is an object of the present invention to provide a, novel and improved method of bleaching tion is shown. This bleaching machine includes a large drum designated as an entirety by the letter A and having an upper cylindrical portion 6 closed at its upper end by a cover plate I. The lower end of the cylindrical portion 6 of the drum is connected to two dividing trunks 8 each of which has outer half conical walls 8a and inner walls 8b which extend downwardly from a transverse medial line running fore and aft of the drum A at the lower part of the cylindrical portion 5 and which walls 8b are also curved in horizontal cross section and taper from their upper edges to their lower edges. The walls of the dividing trunks 8 are quite steep so as to prevent the lodging of flour thereon. At their lower ends the dividing'trunks are of elliptic shape as flour by use of a gaseous bleaching medium which will thoroughly and intimately bring the bleaching gas into contact with the fine particles of the flour to produce a uniform and thorough bleaching action without over-treatment.

Another object is to provide a novel and improved bleaching process and apparatus for bleaching flour which, respectively, can be carried on and operated continuously without shut down periods and without necessity for cleaning out the apparatus and which will eliminate the possibility of over bleaching of any part of the shown in Fig. 4 and they join collecting trunks 9 at their lower ends which collecting trunks run down diagonally toward each other to join and form an outlet mouth III. This mouth Ill delivers into a horizontally disposed cylindrical conveyor casing Ii which runs to one side of the drum A and is in turn equipped with an outlet l2. The central portions of the walls 81) of the dividing trunks are not joined and a boxlike bearing bracket l3 joins these walls at this v point for a purpose presently to be described.

A flour chute H for feeding flour into the drum A is mounted centrally in the cover plate I and lowing description made in connection with the accompanying drawings, wherein like reference characters refer to the same or similar parts throughout the various views, and in which- Fig. 1 is a view in front elevation of anapparatus made in accordance with the present invention for carrying out the processes of the invention.

Fig. 2 is a view in side elevation of the same the lower adjacent part of the feed spout in dotted lines.

Referring to the drawings, a typical device for carrying out the processes of the present invenlarge fan 22 the blades of which are pitched relprojects downwardly into the cylindrical portion.

6 of the drum A. This chute I4 is preferably provided at its lower end with a telescoping chute extension Ma whereby the level of the lower end of the chute is capable of adjustment. A bracket 1 5 is secured to the two walls 8b below the box-like bracket i3 and the bracket l3 carries on its upper side a thrust bearing i6 within which a an upwardly extending vertical shaft I1 is Journaled. This shaft i1 is also journaled in a bearing [8 secured to the underside of the top of the box-like bracket IS. The shaft is packed by Packing i 9 at the point where it emerges from the box-like bracket l3 and the shaft extends upwardly to a point adjacent to but spaced slightly below the lower edge of the extension Ha of the chute it.

At its upper end the shaft i1 carries a shallow rotating dish 20 which is provided with the serrations or teeth 2! at its upper edge as best shown in Fig. 6. The lower end of the chute extension Ila extends into the dish 20 to a'point adjacent to but spaced upwardly somewhat from the bottom of the dish.

Secured to the shaft ll below the dish 20 is a mouth l8 to the mouth l2.

ative to the direction of rotation of the shaft l1 so that the fan will force a blast upwardly from below the dish 28. A pair of gas pipes 23 for the admission of bleaching gas are mounted in the top plate 1 of the drum and these pipes are supplied with the bleaching gas from any suitable source of supply as through hoses 24. Gases that may be employed for the purpose are chlorine, nitrogen trichloride, oxides of nitrogen, etc. and it is contemplated that one or a mixture of such gases will be used in connection with the present machine and process.

In order to suitably support the drum A a stand consisting of four legs 25, side cross bars 26 and front and rear cross bars 21 is provided, said legs being attached by suitable brackets 28 to the dividing trunks 8 of the drum A. At the front of the machine a driving shaft 29 is provided and this shaft is journaled in suitable bearings 38 carried by the two front legs 25. This shaft is adapted to be driven as by a belt (not illustrated) from any suitable source of power and the belt will run over a pulley 3| carried by the shaft 29 at one end thereof. The shaft 29 is locatedadjacent the lower end of the shaft l1 and the shaft 29 carries a vertical pulley 32 over which a belt 33 travels, this belt also running over' a horizontal pulley 34 carried by the shaft I1 between the walls 81: adjacent the lower end of the shaft.

Journaled in a bearing 35 carried by the side bar 26 and also journaled in suitable bearings 36 carried at the ends of the conveyor casing II is a horizontal conveyor shaft 31 which extends from the left side of the machine as shown in Fig. 5 through the conveyor casing H. shaft is driven from the left end of the shaft 29 as viewed in Fig. 1 by means of a pulley 38 carried by the-shaft 29, a pulley 39 carried by the shaft 21 in alignment with the pulley 38 and an endless belt 68 running over the two pulleys 38 and 39. Within the conveyor casing H the conveyor shaft 31 carries a plurality of pitched vanes 4| and the direction of rotation of the shaft 31 is such relative to the pitch of the vanes 4| that these vanes will work the flour from the Extending into the conveyor casing H from the mouth I8 is a partition 42 which runs downwardly across the upper portion of the casing to a point about midway be-' tween the top and bottom thereof and between a pair of the vanes M, the said partition being notched to receive the conveyorshaft Ell. Another partition 43 runs down in similar manner adjacent to but spaced to the left of the outlet l2 as viewed in Fig. 5.

When the bleaching machine is in operation the bleaching gas is delivered into the drum A from the pipes 23 preferably into the upper, part of the drum. Flour is delivered through the chute and its extension Ha on to the dish 28. The dish 20 rotates at high speed and as the flour is received by the dish it is thrown off cen- This viding trunks 8 and is then collected by the collecting trunks 9 to dischargefrom the mouth l8 into the conveyor casing l I. The conveyor, consisting of the shaft .31 and the vanes ll, is rotated at such speed relative to the quantity of flour delivered thereto that the flour in the casing II will always more than half fill the conveyor casing H and accordingly the partition 42 will seal off the drum A at its lower ends so that the bleaching gas cannot escape through the conveyor casing II. To be doubly sure of sealing off the lower end of the drum A asecondary partition 43 is provided. The flour working into the casing I I is moved by the vanes ll to the right, as viewed in Fig. 5, outlet mouth l2.

With the arrangement shown the flour is broken up into a flne shower with the individual particles in detached relation and acted on by i the bleaching gas and it delivers out ofthe drum A without in any way clinging to the drum. By 7 reason of the fact that the flour cannot cling to the drum it cannot build up thereon to be, overtreated, by the bleaching gas and to require frequent clean out of the drum. Also by reason of the fact that the flour cannot build up in the made in the form, details, arrangement and pro-.

portions of the various parts of the bleaching machine without departing from the scope of the invention which generally stated consists in the matter shown and described and set forth in the trifugally by the dish and the serrated teeth 2| act in throwing on the flour to break it up and divide it. The fan 22 working below the dish 28 throws up a blast into the flour thrown out centrifugally by the dish 28 and this blast further sists in centrifugally throwing the flour outwardly from a central point and forcing the thrown out flour into a gaseous bleaching medium by a blast which divides the thrown out flour into fine particles individually detached one from another.

3. The process of bleaching flour which consists in centrifugally throwing the flour outwardly from a central point and subjecting the thrown'out flour to an upwardly directed blast 'through centrifugal action, further subdividing the flour by wind action introduced below the central point and introducing into the chamber a gaseous bleaching agent.

5. The process defined in claim 4, the bleaching agent employed being chlorine gas.

6. The process defined in claim 4, the bleaching agent employed being nitrogen trichloride I and discharged through themoms:

'1. The room deflnod ln oioim 4, the bleachine agent employed boinl o Iueouo oxide 0! nito the chamber abovethe point of introduction of the flour. disseminating the flour outwardly from its point of introduction inn, leneraliy horizontal piene through eentrimeifaction-end 1111' ther subdividing the flour Ihlle it 1M0 the bleaching medium by an upward blast from below the point of introduction of the flour and collecting and removin'rthe bleached hour from the chamber. i

I; The process oi bleoohin: .ilour which conliltl in introduoinz theflour into a. chamber. introducing ouoaeoul bloechinl medium. into the chamber, diueminotin: the flour outwardly from its point of introduction in a senerally horizontal plane through centrifugal action, further subdividing the flour by an: upward blast of the bleaching medium from below the point of in,- troduction, coileetingnnd removing the bleached flour: flW/preveritine the escapee! the bleaching from i the. A by; the. flour being removed ti'ieretr m'h;

t H"Mc DONAI.-D. 

